Invasion
Invasion Description
1st Record: Brisbane, San Mateo County/CA/San Francisco Bay (9/5/2000, Gosliner and Behrens 2006)
Geographic Extent
CA/Tomales Bay (2008, Hanson et al. 2012); Brisbane, San Mateo County/CA/San Francisco Bay (9/1999, Gosliner and Behrens 2006) Oakland/CA/Lake Merritt (11/1/2003; Gosliner and Behrens 2006; Australian Museum 2006); Sierra Point Marina, San Mateo County/CA/San Francisco Bay (Cohen et al. 2005); Brisbane Lagoon, San Mateo County/CA/San Francisco Bay (Cohen et al. 2005); Fruitvale Bridge, Alameda County/CA/Oakland Estuary (Cohen et al. 2005); Sierra Point Marina, San Mateo County/CA/San Francisco Bay (Cohen et al. 2005); San Leandro Marina/CA/San Francisco Bay (Cohen et al. 2005); Pete's Harbor, San Mateo County/CA/San Francisco Bay (Cohen et al. 2005); Coyote Point/San Mateo County/CA/San Francisco Bay (Cohen et al. 2005)
Vectors
| Level | Vector |
|---|---|
| Alternate | Ballast Water |
| Alternate | Oyster Accidental |
| Probable | Hull Fouling |
Regional Impacts
| Economic Impact | Health | |
| Cercaria of an unidentified schistosome trematode Gigantobilharzia sp. associated with H. japonica have been a cause of swimmers itch (cercarial dermatitis) among bathers in San Francisco Bay. The larvae burrow into human skin, causing inflammation, but are unable to complete metamorphosis. Their normal hosts are shorebirds. The trematode appears to be exotic to North America, and first began infecting people in the late 1990s, most likely introduced from elsewhere (Anonymous 2005; Cohen 2005; Brant et al. 2010). | ||
| Ecological Impact | Competition | |
| The native H. vesicula is reported to have declined in areas invaded by H. japonica. (Hanson 2012). However, the details and locations of these observations were not given. | ||